1. Field of the Invention
The present invention relates generally to an optical storage device, and more particularly to an objective lens driving mechanism in an optical storage device.
2. Description of the Related Art
An optical disk has received attention as a memory medium that becomes a core in the recent rapid development of multimedia, and it is usually accommodated in a cartridge case for practical use. The optical disk is loaded into an optical disk drive to perform reading/writing of data from/to the optical disk by means of an optical pickup (optical head).
A recent optical pickup of an optical disk drive intended to realize size reduction is composed of a fixed optical assembly including a laser diode, a beam splitter for reflecting and transmitting a laser beam, and a photodetector for receiving reflected light from an optical disk, and a movable optical assembly including a carriage, an objective lens mounted on the carriage, and a focusing mechanism having a support member for the objective lens and a focusing coil.
The objective lens is supported by a lens holder. The lens holder is supported to the carriage by two metallic parallel leaf springs in a cantilever fashion. A pair of focusing coils are fixed to the lens holder, and a pair of focusing magnetic circuits are mounted on the carriage so as to respectively face the pair of focusing coils fixed to the lens holder. Each focusing magnetic circuit supplies a magnetic flux to the corresponding focusing coil carrying a current to thereby apply an electromagnetic force to the lens holder along the optical axis of the objective lens, thus driving the objective lens along its optical axis.
The carriage is movable in the radial direction of the optical disk as being guided by a pair of guide rails by a carriage driving mechanism. The carriage driving mechanism includes a pair of carriage driving coils fixed to the opposite side surfaces of the carriage and a pair of carriage driving magnetic circuits mounted on a base along the opposite side surfaces of the carriage. Each carriage driving coil is partially inserted in a gap defined in the corresponding carriage driving magnetic circuit. When the carriage driving coils are energized, an electromagnetic force is applied to the carriage to thereby drive the carriage in the radial direction of the optical disk.
With this arrangement, the focusing mechanism performs focusing control of the focal position of the objective lens so that the focal point of the objective lens always lies on a fluctuating recording surface of the optical disk. Further, the carriage is driven by the carriage driving mechanism to move the objective lens in the radial direction of the optical disk to an arbitrary track on the optical disk (seek control). Further, the carriage driving mechanism performs tracking control such that the focal position of the objective lens always follows a desired track whose position is fluctuated in the radial direction of the optical disk by the vibrations of a spindle motor or by off-centering upon chucking the optical disk.
A write-power laser beam emitted from the laser diode of the fixed optical assembly is first collimated by a collimator lens, next transmitted by the beam splitter, next reflected by a beam raising mirror, and finally focused on the optical disk by the objective lens, thereby writing data onto the optical disk. On the other hand, data reading is performed by directing a read-power laser beam onto the optical disk. Reflected light from the optical disk is first collimated by the objective lens, next reflected by the beam splitter, and finally detected by the photodetector, thereby converting the detected optical signal into an electrical signal.
In such a conventional objective lens driving mechanism, a flexible printed circuit board (FPC sheet) is longitudinally placed on the leaf springs supporting the lens holder in a cantilever fashion, so as to feed a current to the focusing coils fixed to the lens holder (Japanese Patent Laid-open No. Hei 6-176384). This conventional current feed structure for the focusing coils has a problem such that its assembling work is troublesome. Further, the thickness of each leaf spring formed of stainless steel is about 20 xcexcm, whereas the thickness of the FPC sheet is about 40 to 60 xcexcm and it has rigidity to some extent. Accordingly, there is a problem that variations tend to occur in frequency characteristics, mechanism characteristics such as drive sensitivity, and lens tilt characteristics of the objective lens driving mechanism, depending on a formed condition of the FPC sheet.
It is therefore an object of the present invention to provide an objective lens driving mechanism in an optical storage device which can improve the assembly workability and stabilize the mechanical characteristics.
It is another object of the present invention to provide an optical storage device which can achieve high-precision positioning of the focal point of the objective lens to thereby realize high-density recording and/or reproduction of information.
In accordance with an aspect of the present invention, there is provided an optical driving device including an objective lens for focusing a light beam onto an object; a lens holder having the objective lens; a platelike conductive elastic support member having one end for supporting the lens holder and the other end having a first terminal portion; a fixing member for fixing the other end of the platelike conductive elastic support member; a coil electrically connected to the platelike conductive elastic support member and fixed to the lens holder; and a flexible printed circuit board connected to the first terminal portion of the platelike conductive elastic support member.
The platelike conductive elastic support member further has a second terminal portion connected to the coil. Preferably, the first terminal portion of the platelike conductive elastic support member is provided at a position facing a land of the flexible printed circuit board at right angles to the land.
Preferably, the lens holder has a guide for guiding a lead from the coil toward the second terminal portion of the platelike conductive elastic support member. More preferably, the first terminal portion extends in a longitudinal direction of the platelike conductive elastic support member, and the second terminal portion extends in a transverse direction of the platelike conductive elastic support member. Preferably, the platelike conductive elastic support member includes a pair of first and second conductive leaf springs arranged in parallel.
In accordance with another aspect of the present invention, there is provided an optical storage device capable of at least reading information recorded on an optical storage medium, including a carriage adapted to be reciprocated in a given direction of the optical storage medium; driving means for reciprocating the carriage in the given direction; an objective lens for focusing a light beam output from a light source onto the optical storage medium; a lens holder having the objective lens; a platelike conductive elastic support member having one end for supporting the lens holder and the other end having a first terminal portion; a fixing member mounted on the carriage for fixing the other end of the platelike conductive elastic support member; a coil electrically connected to the platelike conductive elastic support member and fixed to the lens holder; and a flexible printed circuit board connected to the first terminal portion of the platelike conductive elastic support member.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.